Transgenic technologies are prohibitively expensive for individual laboratories and require extremely skilled and dedicated personnel and institutional support. This is because first, many factors greatly affect expression levels of randomly inserted DNA, which leads to transgenes being transcriptionally silent at many chromosomal locations. In addition, there is a considerable risk as to whether targeted ES cells will contribute to the germline. As a result, no transgenic facility will guarantee transgene expression, nor that targeted ES cells will go to germline. Secondly, many investigators whose studies require the use of transgenic animals are not trained in their generation. This is partly the case for this program project where the expertise of investigators and their lab personnel range from extensive experience to very little experience. Therefore, the expertise that is available in the transgenic core at UMKC has also been included in this program project. The Director and Co-Director will assist the principal investigators in the design of constructs, educate personnel and students, and oversee the general operation of the core. The services of this core will not only be to generate transgenic mice, but to cross breed mice to generate the correct genotype, and to maintain the mice until ready for the Mechanical Strain Core or to be sent to the investigator. The purpose of this core is to provide efficient and economical service to the members of the Program Project plus the needed educational component. The core will also provide the following: 1) generation of transgenic embryos for screening of expression of Dmp1 and Mepe promoter fragments for osteocyte selectivity and response to mechanical load;2) generation of transgenic mice expressing the 8 and/or 10 kb Dmp1-Cre, intact MEPE or MEPE promoter fragments, 3). generation of wild type Cx43 and truncated Cx43 mice and their targeted expression in osteocytes;4) generation of Dmp1-loxP and E-11-loxP mice;5) generation of floxed mice lacking Dmp1 or E11 in osteocytes using various promoters regulating Cre expression;and 6) maintainance of all Cre mice needed for this project, including osteocalcin-Cre, 8 (and/or 10) kb Dmp1 Cre, and 3.2 kb Col 1a1 ERt2-Cre mice. In addition, the Core will serve as a resource for consultation and training for prinicipal investigators, their students and personnel for genotyping and screening of transgenic and knockout mice.